How To Address Vascular Complications With Lower Extremity Wounds
Our contemporary knowledge and critical limb ischemia (CLI) tools have allowed us to dispel many myths regarding the endovascular treatments of lower extremity disease and CLI. These tools are not perfect but they have greatly improved over the last decade and certainly over the last two to three years. One of the biggest complaints I hear from podiatrists is “the surgeons and interventionalists in my area do not believe these things work.” Accordingly, let us take a closer look at some of these myths and the corresponding realities.
Myth: Most CLI patients get an appropriate vascular assessment. In 2008, one would hope that most, if not all, CLI patients would have at least an objective non-invasive vascular evaluation before primary amputation occurs. This is simply not the case. Likewise, most patients with diabetic foot ulcers (DFUs) and poorly healing lower extremity wounds should undergo a thorough noninvasive vascular evaluation. Unfortunately, this often does not occur. A physical exam and palpable pedal pulses are usually adequate to ensure pedal blood flow.
However, a patient can still lose a foot with a palpable pulse and a palpable pulse does not always ensure adequate blood flow. Patients can have chronic total occlusions (CTOs) of the femoral or infrapopliteal vessels, and still have a palpable pulse.
When it comes to most lower extremity wounds, the use of appropriate wound care and adequate revascularization should facilitate significant progress toward healing in three to four weeks. If this does not occur, it should be mandatory to obtain a formal vascular consultation with at least an ankle brachial index (ABI) and a duplex arterial ultrasound. Bear in mind that ABIs can be falsely elevated and appear normal in patients with diabetes due to vascular calcification. A duplex ultrasound is better but it is not perfect. In my experience, the new multislice 16-64 channel CTA has now become the “gold standard” for vascular imaging and is the best of all non-invasive vascular imaging modalities for lower extremity arterial assessment.
Published protocols and data are sparse when it comes to assessing how CLI patients are managed.There are few consensus protocols. In 2004 and 2005, I became strongly suspicious that the majority of CLI patients received an inadequate vascular evaluation and many received referrals for primary amputation without vascular evaluation. At that time, many new “endovascular tools” for complex lower extremity revascularization were under development.
In a retrospective analysis drawn from Medicare database information on a Midwest patient population of 2.5 million CLI patients treated between 2002 and 2003, we analyzed the Medicare data on 417 CLI patients. Our goal was to evaluate how CLI patients were treated and what medical specialties were consulted. We analyzed all data over an 18- month period of time beginning with the index diagnosis.1
Shockingly, 67 percent of those 417 CLI patients had an index treatment of primary amputation. Only 16 percent had traditional angiography and only 35 percent had an ABI. Therefore, greater than 50 percent of these CLI patients had a vascular evaluation. Only 26 percent had a vascular surgery consultation and 21 percent had a cardiology consultation. The overall complication rate and the incidences of myocardial infarction and death and stroke were significantly greater in the 67 percent of patients who had a primary amputation versus 33 percent of CLI patients who had a vascular evaluation, and a cardiology or vascular surgery consultation.1
Hopefully in 2008, practitioners obtain appropriate vascular evaluations more frequently in the United States and worldwide than five years ago.We have no confirmatory evidence but over the last several years, there have been many multidisciplinary efforts to enhance the overall awareness of CLI. An increased awareness of the availability of new minimally invasive endovascular techniques for lower extremity revascularization should result in fewer patients being referred for a primary amputation and more patients being referred for a non-invasive vascular evaluation to identify candidacy for minimally invasive endovascular or surgical revascularization.
In my practice, all patients receive at least a non-invasive lower extremity computed tomography angiography (CTA) and greater than 95 percent will have some revascularization option. No patient should have a primary amputation in 2008 without at least a vascular consultation and non-invasive vascular evaluation, preferably with CTA.
Have New Advances Changed The Perception Of Certain Vascular Procedures In The Lower Extremity?
Myth: Balloon angioplasty and stenting do not work in the lower extremity. That myth may have been somewhat appropriate in the 1990s. Balloon and stent technology were new and we utilized inadequate cardiac technology for the lower extremities. Technology began to improve between 2000 and 2005, and we have seen the emergence of data reflecting the improved technologies.
Over the last two to three years, significant technological advancements and data are available that easily dispel this myth. Adjunctive technologies, including pharmacological support, novel wire and crossing technologies, now make it possible to achieve a CLI procedural success rate of 96 to 97 percent with contemporary balloon and stent technology respectively.There are now refined low profile balloons with lengths up to 200 mm and current dedicated infrainguinal and infrapopliteal stent technology have greatly improved.
Improved technology has adequately addressed stent fractures, one of the major problems with stenting. Earlier stent designs suffered from fracture rates approaching 50 percent. The recent results of the RESILIENT trial have identified a less than 5 percent fracture rate at 12 months in a randomized trial versus angioplasty.2 Stents are not perfect but they are improving. New stent designs have less than a 1 percent fracture rate and will also be highly kink resistant. Novel balloon and specialty balloon technology are emerging with specialized cutting surfaces and drug coatings.
The results of the recently published THUNDER trial, a drug coated balloon trial, revealed greater than 85 percent 12- month patency. In general, the most recent superficial femoral artery (SFA) stent data also has more than 80 percent 24-month patency.3-4
In 2008, it is clear that balloon angioplasty and stent technology work in the lower extremity. The randomized BASIL trial found endovascular therapy to be equivalent to fem-pop bypass at three years.5
I believe we have convincing evidence today that endovascular technologies do work in the lower extremity. Remember, these are minimally invasive, local anesthetic cases that are often outpatient procedures with a high likelihood of success and very low risk to the patient. Even if there is an attrition rate or failure rate of approximately 15 to 20 percent at two years, these procedures are easily repeatable and reproducible. Indeed, this is one of the great advantages of endovascular treatment.
Myth: Nothing works below the knee except tibial bypass surgery. Like the previous myth, this myth was unquestionably true in the 1990s and had some merit up until approximately three to four years ago.Today, interventionalists and industry have worked together to provide an excellent “infrapopliteal CLI toolbox.” Yes, tibial bypass surgery is an excellent procedure in the appropriate candidate.
Unfortunately, many of these older patients have risks for general anesthesia and many have no available saphenous vein. Creative tibial bypass procedures can still be successful via a wide array of novel creative surgical techniques but they require an experienced, creative and committed surgeon. Tibial bypass procedures are not perfect and approximately 20 percent will fail or need revision or “endovascular salvage” within 18 months. This underscores the importance of having both an interventionalist and surgical component to the revascularization resources of the limb salvage team.
Early coronary wire, balloon and stent technology simply did not work well in the infrapopliteal vessels. Today, a multitude of new wires and crossing technologies allow vascular interventionalists to cross greater than 95 percent of all infrapopliteal vessels and CTOs. The inability to cross CTOs was once the main reason for endovascular failure, bypass surgery, amputations and an overall “unwillingness” to attempt infrapopliteal revascularization. We can now cross these lesions and follow with emerging definitive therapies that include various atherectomy devices, low profile specialty balloons and dedicated infrapopliteal stents. Long, compliant, small low profile balloons are available and interventionalists can now perform revascularization into the pedal vessels on a routine basis.
Optimal vessel sizing and vessel interrogation are now possible in the infrapopliteal vessels, very similar to the way coronary arteries have been treated for two decades. Researchers have reported excellent results in utilizing the very successful drug-eluting coronary stents in the infrapopliteal vessels.6 Studies have reported low restenosis rates utilizing infrapopliteal stents with a “coronarylike” strategy.
I believe we have now entered an era in which we will be “treating the infrapopliteal vessels like we treat the coronary vessels.”As more sophisticated ways to treat infrapopliteal vessels become feasible in treating our CLI patients, it only bodes for continued improved outcomes utilizing endovascular techniques.
Setting The Record Straight On Endovascular Interventions In Patients With CLI
Myth: There is no data supporting endovascular interventions in CLI. Again, this may have been true a decade ago but not in 2008. As early as 2001, Doros reported excellent limb salvage rates using balloon angioplasty only in a time when we had few CLI tools.7
In 2006, the landmark LACI trial involved 151 CLI patients with no surgical options who were all doomed for amputation. This multicenter international study utilized excimer laser therapy and reported an excellent 93 percent six-month limb salvage rate and only a 7 percent amputation rate in these patients, who were likely looking at a 100 percent amputation rate.8 A very elderly high-risk patient population safely underwent these procedures with no major complications and researchers cited only a 12 percent re-intervention rate at six months.8 Subsequent studies showing excimer laser results include the Belgium LACI trial and our own CIS LACI trial, which reported 85 to 90 percent 12- month limb salvage rates with excimer laser therapy.9-10
Studies report greater than 85 percent 12-month limb salvage rates with plaque excisional atherectomy, cryotherapy, cutting balloon, the AngioSculpt specialty balloon (AngioScore), PTA, bare metal stenting and drug-eluting coronary stents.6-14 In 2008, we unequivocally have adequate to excellent data reporting excellent limb salvage rates in CLI patients treated with endovascular infrapopliteal revascularization techniques.
Are Endovascular Procedures Viable Alternatives To Amputation In Elderly Patients?
Myth: Endovascular procedures are too risky in old, sick patients, making primary amputation the procedure of choice. It is estimated that surgeons perform between 220,000 and 240,000 major and minor lower extremity amputations in the U.S. and Europe yearly for CLI.15-19 In the U.S., the amputation rate has increased from 19 per 100,000 people/year to 30 per 100,000 people/year over the last two decades, primarily due to an increase in diabetes and advancing age.6-7 Despite advances in cardiovascular treatment, in patients over the age of 85, researchers have reported an amputation rate of 140 per 100,000 people/year with a primary amputation still carrying an excessively high mortality rate of 13 to 17 percent.7-9
In the highest risk patients, 30-day periprocedural mortality after amputation can range from 4 to 30 percent and morbidity ranges from 20 to 37 percent because many end-stage CLI patients will suffer from sepsis, progressive renal insufficiency and other significant medical comorbidities.8,10
The aforementioned LACI trial was one of the first landmark trials that showed that we could utilize endovascular revascularization in the highest risk elderly patient population with less than 2 percent major mortality and morbidity.8 Multiple additional reports have recently reported similar low risks during endovascular revascularization. This is extremely significant because the 30-day periprocedural mortality and morbidity (M&M) rates after a primary amputation are significantly higher than the M&M rates reported with endovascular therapy and range between 20 and 37 percent.20-22
Remember, these are elderly patients who, by the time they have an amputation, are often septic, in renal failure, are at high-risk for general anesthesia, are already set up for poor wound healing after amputation, and are generally a very high-risk patient population.
Keep in mind that endovascular therapies occur with the patient under local anesthesia. Often, this involves a single needle stick in the groin. These procedures are not associated with incisions and healing, and are truly minimally invasive to the patients. Accordingly, one sees major and minor complication rates of less than 3 to 4 percent.Without question, the current risks involved with endovascular revascularization are low and much less than the risks associated with having a primary amputation.
Dispelling Myths About Infrapopliteal CTOs In Patients With Diabetes
Myth: Most patients with diabetes have complex infrapopliteal CTOs that cannot be treated. It is true that over 90 percent of patients with diabetes have complex infrapopliteal CTOs. However, as I previously noted, vascular interventionalists can now cross and treat CTOs. The real myth here is that it has been taught that all infrapopliteal and pedal vessels become totally obliterated with diabetes. Therefore, there are no “distal targets” for either a tibial bypass or for endovascular treatment into a patent pedal vessel below the ankle.
Most patients with diabetes who do suffer from severe infrapopliteal CTOs have the phenomenon of “pedal sparring.” This refers to the fact that the dorsalis pedis artery (DPA) and/or posterior tibial artery (PTA) below the level of the ankle will often be free of obliterative disease. These arteries are patent and be perfused by a collateral artery network, revealing a “distal vascular target” appropriate for revascularization. This presents an opportunity for either surgical or endovascular revascularization.
This becomes very important with committed limb salvage angiography and during CTA. If physicians are not aware of this “pedal sparring,” they will not consider revascularization and their imaging will be inadequate. Patients often receive referrals for primary amputation when they actually have the potential for revascularization.
Should You Refer Patients With Poor Renal Function For Endovascular Procedures?
Myth: One cannot and should not perform endovascular procedures on patients with poor renal function. This is an important myth to dispel because deteriorating renal function is a function of age and our CLI patient population is generally elderly with very high incidences of diabetes and preexisting renal insufficiency. When considering the overall poor outcome after an amputation, with less than 50 percent being alive at three years, it becomes imperative to develop strategies to allow us to perform endovascular therapies even in the face of renal dysfunction.
If not, we will leave many patients untreated. Remember that as a CLI limb progresses and deteriorates, the limb is toxic to the kidney itself in the form of sepsis and circulating tissue factors, such as myoglobin and hemoglobinuria, are extremely toxic to the kidney. Likewise, many of the antibiotics used to treat CLI further diminish renal function. Therefore, it becomes compelling to treat these patients aggressively with endovascular therapies.
Today, we have multiple techniques to optimize and minimize contrast utilization during CLI interventional strategies. This diminishes the likelihood of worsening renal insufficiency and, in many cases, improves renal function. Renal hydration protocols and other pharmaceutical approaches are now available to support renal function during contrast utilization. We have devices that allow us to deliver contrast more efficiently during our procedures. The use of preoperative magnetic resonance angiography (MRA) and CTA — which is an intravenous contrast dose that is much less toxic than intraarterial doses — allow us to plan our procedures better and accordingly use much less toxic intra-arterial contrast during our endovascular therapies.
In particular, the use of CTA has also helped us identify a very large portion of patients who have renal artery stenosis.We frequently will simultaneously perform renal artery PTA/stenting that can greatly improve renal function. Many of our new “CLI tools” also allow for much quicker procedures, which facilitate much less contrast exposure. A novel bifurcated catheter allows simultaneous infusion of renal artery vasodilators both peri- and post-procedural that will increase renal blood flow and decrease the incidence of contrast-induced nephropathy (CIN) by utilizing targeted renal therapy (TRT).
In short, we currently have multiple strategies, which do allow for successful endovascular treatments in even the patients at highest risk for CIN. Therefore, I see little justification for not moving forward with limb salvage procedures in patients with poor renal function. We have learned a lot about CIN over the last few years and I personally believe we should offer these minimally invasive limb salvage techniques in patients with known renal dysfunction.
Addressing Concerns About Distal Embolization
Myth: Distal embolization rarely occurs during endovascular treatments. This is a myth that interventionalists have to dispel among our referring colleagues and ourselves. The atheroscle- rotic burden within the SFA, popliteal and infrapopliteal arteries can be significant. With aggressive endovascular manipulations, it only stands to reason that some of this material can embolize into the pedal microcirculation. In turn, this would make a patient with either rest pain or CLI worse while improving more proximal blood flow.
This is very analogous to the embolic debris that can generate during carotid stenting. Accordingly, we have seen the development of distal protection devices (DPD) or small basket-like filters that vascular interventionalists can place in the distal cerebral circulation. These devices allow a more proximal endovascular intervention in the carotid artery.We can now utilize these DPDs in the vessels of the lower limb.They allow us to be more aggressive with endovascular therapies with a distal “safety net” to retrieve any embolic material that could travel into the pedal microcirculatory circulation.
These DPDs are small filter-like devices that are available in sizes between 3 and 7 mm. Vascular interventionalists can easily place them into the popliteal or infrapopliteal vessels, which facilitates more proximal interventions.
It is likely that we have underestimated this phenomenon of distal embolic debris over the years because we have had no objective assessments of the pedal microcirculatory anatomy or function. There are several exciting new technologies that physicians are utilizing in wound care and for the assessment of amputation levels that will hopefully help us identify the true impact of distal embolization.
Several emerging technologies are being developed to assess wound healing and they hold promise for evaluating pedal microcirculatory function pre- and post-endovascular intervention.
The OxyVu (HyperMed) uses medical hyperspectral imaging, a camera-based diagnostic tool that quantifies hyperspectral tissue oxygenation in diabetic foot ulcer wound healing. This technology has the potential to facilitate objective assessment of pedal microcirculatory disease and function. The Sensilase System (Vasamed) is a laser Doppler exam that combines skin perfusion pressure (SPP) and pulse volume recording (PVR) to assess the wound healing and access capillary circulation. It also helps predict the level of amputation. Both technologies are under investigation and may show promise as objective physiologic assessments of pedal microcirculatory function. They may help define the clinical role of distal embolization associated with endovascular interventions. I have lowered my threshold for using DPDs in patients with advanced lower extremity disease and especially CLI. Many of my colleagues are likewise doing so and I predict this will expand our therapies and further improve our endovascular outcomes in patients with CLI.
Defusing Other Myths About Endovascular Procedures
Myth: One cannot treat infrapopliteal or infrapedal vessels via endovascular procedures or stenting. Over the last several years, endovascular labs across the country have dispelled this myth every day. Using contemporary crossing technology, vascular surgeons can now cross greater than 95 percent of all infrapopliteal and pedal lesions. Dedicated infrapopliteal stents are available.
Several recent studies have shown that both bare metal stents and drug-eluting stents work extremely well in the CLI patients when vascular interventionalists utilize them in infrapopliteal vessels. One can now liberally use specialty balloons and stents in most infrapopliteal and even some pedal vessels down to 2.0 to 2.25 mm in diameter.
Even lower profile atherectomy technologies are available that allow endovascular interventions below the ankle and to the pedal, or what I have termed “infrapedal”vessels.Vascular interventionalists can now deliver coronary wire-based 0.014-mm wires even into digital vessels.
The 0.9 excimer laser probe, which has been available for several years, allows pedal atherectomy and revascularization. The new MiniHawk plaque excisional device (ev3) is now less than 2 mm in diameter and can infiltrate into pedal vessels. The recently available Diamondback 360 orbital atherectomy device (Cardiovascular Systems) also has a very low profile.Vascular interventionalists can utilize this device in infrapopliteal and pedal vessels with this design being particularly helpful in those highly calcified vessels that we see in diabetic and dialysis patients.
Myth: All bypass surgeries last forever and all endovascular treatments fail miserably. I have previously addressed the latter myth by providing data that now shows endovascular therapies are highly successful in patients with CLI. Often, revascularization over even a short six- to 12-month period of time is adequate to allow wound healing and limb salvage.This may even be the case if the endovascular therapy fails.
Femoral–tibial bypass surgery has been and continues to be an excellent therapy. It is indeed a cornerstone in every limb salvage program. Bear in mind that tibial bypass grafts have a 15 to 20 percent attrition rate over 12 to 24 months. Many of our patients today require creative tibial bypass grafts with less than optimal conduits. All endovascular and surgical therapies require close clinical and objective follow-up surveillance.
In my practice, it is common to see a patient in whom we have performed several endovascular therapies over a five- to six-year period of time for limb salvage. The patient would subsequently require a femoral to tibial bypass graft and the next CLI episode would occur after endovascular therapies have failed. Note that 20 to 30 percent of all limb salvage patients will need a second endovascular limb salvage procedure within 18 months. In such patients, the tibial bypass graft will now have an 80 percent patency at approximately 18 to 24 months.
We have learned to perform aggressive graft surveillance and we will often identify graft problems such as kinking, anastomotic intimal hyperplasia, vein graft valve lesions, etc.Vascular interventionalists would then salvage these grafts by utilizing endovascular techniques such as specialty balloons, stents, etc.
There are currently no cures for diabetes or atherosclerotic disease. Accordingly, it is imperative that endovascular techniques and other surgical options are available to all patients suffering from CLI. We can often provide an endovascular therapy to save a limb, a fem-tib bypass to remedy an endovascular failure and an endovascular therapy to salvage a failing graft.This is the dedicated vascular commitment necessary to achieving limb salvage over a long period of time.
Dr. Allie is the Chief of Cardiothoracic and Endovascular Surgery at the Cardiovascular Institute of the South in Lafayette, La. The author thanks Kelly M.Tilbe for her assistance with technical manuscript preparation.
Editor’s note:The fourth international multidisciplinary CLI Summit will be held on September 11 in New Orleans as a component of the larger New Cardiovascular Horizons (NCVH) conference. The ninth annual NCVH meeting will be held from September 10-13, 2008.
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